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Sat, 16 Sep 2000 00:00:00 +0200Sat, 16 Sep 2000 00:00:00 +0200Bloch particle in presence of dc and ac fields: Statistics of the Wigner delay timehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1165
The paper studies quantum states of a Bloch particle in presence of external ac and dc fields. Provided the period of the ac field and the Bloch period are commensurate, an effective scattering matrix is introduced, the complex poles of which are the system quasienergy spectrum. The statistics of the resonance width and the Wigner delay time shows a close relation of the problem to random matrix theory of chaotic scattering.Markus Glück; Andrey R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1165Sat, 16 Sep 2000 00:00:00 +0200A truncated shift - operator technique for the calculation of resonances in Stark systemshttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/870
A novel method is presented which allows a fast computation of complex energy resonance states in Stark systems, i.e. systems in a homogeneous field. The technique is based on the truncation of a shift-operator in momentum space. Numerical results for space periodic and non-periodic systems illustrate the extreme simplicity of the method.Markus Glück; A. R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/870Sat, 02 Sep 2000 00:00:00 +0200Bloch particle in presence of dc and ac fieldshttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/879
The paper studies metastable states of a Bloch electron in the presence of external ac and dc fields. Provided resonance condition between period of the driving frequency and the Bloch period, the complex quasienergies are numerically calculated for two qualitatively different regimes (quasiregular and chaotic) of the system dynamics. For the chaotic regime an effect of quantum stabilization, which suppresses the classical decay mechanism, is found. This effect is demonstrated to be a kind of quantum interference phenomenon sensitive to the resonance condition.Markus Glück; A. R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/879Sat, 02 Sep 2000 00:00:00 +0200Chaotic Wannier-Bloch resonance stateshttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/906
The Wannier-Bloch resonance states are metastable states of a quantum particle in a space-periodic potential plus a homogeneous field. Here we analyze the states of quantum particle in space- and time-periodic potential. In this case the dynamics of the classical counterpart of the quantum system is either quasiregular or chaotic depending on the driving frequency. It is shown that both the quasiregular and the chaotic motion can also support quantum resonances. The relevance of the obtained result to the problem a of crystal electron under simultaneous influence of d.c. and a.c. electric fields is briefly discussed. PACS: 73.20Dx, 73.40Gk, 05.45.+bMarkus Glück; A. R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/906Sat, 02 Sep 2000 00:00:00 +0200Stark Resonances in dc fields from short time propagation of the field-free Hamiltonianhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/907
A new method for calculating Stark resonances is presented and applied for illustration to the simple case of a one-particle, one-dimensional model Hamiltonian. The method is applicable for weak and strong dc fields. The only need, also for the case of many particles in multi-dimensional space, are either the short time evolution matrix elements or the eigenvalues and Fourier components of the eigenfunctions of the field-free Hamiltonian.Nimrod Moiseyev; Markus Glück; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/907Sat, 02 Sep 2000 00:00:00 +0200Lifetime statistics for a Bloch particle in ac and dc fieldshttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/908
We study the statistics of the Wigner delay time and resonance width for a Bloch particle in ac and dc fields in the regime of quantum chaos. It is shown that after appropriate rescaling the distributions of these quantities have universal character predicted by the random matrix theory of chaotic scattering.Markus Glück; A. R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/908Sat, 02 Sep 2000 00:00:00 +0200Selective Quasienergies from Short Time Cross-Correlation Probability Amplitudes by the Filter-Diagonalization Methodhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/866
The Filter-Diagonalization Method is applied to time periodic Hamiltonians and used to find selectively the regular and chaotic quasienergies of a driven 2D rotor. The use of N cross-correlation probability amplitudes enables a selective calculation of the quasienergies from short time propagation to the time T (N). Compared to the propagation time T (1) which is required for resolving the quasienergy spectrum with the same accuracy from auto-correlation calculations, the cross-correlation time T (N) is shorter by the factor N , that is T (1) = N T (N).Markus Glück; Hans Jürgen Korsch; Nimrod Moiseyevarticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/866Wed, 30 Aug 2000 00:00:00 +0200Wannier-Stark Ladders in Driven Optical Latticeshttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1058
The paper studies the effect of a weak periodic driving on metastable Wannier-Stark states. The decay rate of the ground Wannier-Stark states as a continuous function of the driving frequency is calculated numerically. The theoretical results are compared with experimental data of Wilkinson et at. [Phys.Rev.Lett.76, 4512 (1996)] obtained for cold sodium atoms in an accelerated optical lattice.Markus Glück; Hankel Michael; Andrey R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1058Fri, 10 Mar 2000 00:00:00 +0100About universality of lifetime statistics in quantum chaotic scatteringhttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1059
The statistics of the resonance widths and the behavior of the survival probability is studied in a particular model of quantum chaotic scattering (a particle in a periodic potential subject to static and time-periodic forces) introduced earlier in Ref. [5,6]. The coarse-grained distribution of the resonance widths is shown to be in good agreement with the prediction of Random Matrix Theory (RMT). The behavior of the survival probability shows, however, some deviation from RMT.Markus Glück; Andrey R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1059Fri, 10 Mar 2000 00:00:00 +0100Induced transitions between Wannier laddershttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1061
We study the transitions between the ground and excited Wannier states induced by a weak ac field. Because the upper Wannier states are several order of magnitude less stable than the ground states, these transitions decrease the global stability of the system characterized by the rate of probability leakage or decay rate. Using nonhermitian resonant perturbation theory we obtain an analytical expression for this induced decay rate. The analytical results are compared with exact numerical calculations of the system decay rate.Markus Glück; Hankel Michael; Andrey R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1061Fri, 10 Mar 2000 00:00:00 +0100Fractal stabilization of Wannier-Stark resonanceshttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1062
The quasienergy spectrum of a Bloch electron affected by dc-ac fields is known to have a fractal structure as function of the so-called electric matching ratio, which is the ratio of the ac field frequency and the Bloch frequency. This paper studies a manifestation of the fractal nature of the spectrum in the system "atom in a standing laser wave", which is a quantum optical realization of a Bloch electron. It is shown that for an appropriate choice of the system parameters the atomic survival probability (a quantity measured in laboratory experiments) also develops a fractal structure as a function of the electric matching ratio. Numerical simulations under classically chaotic scattering conditions show good agreement with theoretical predictions based on random matrix theory.Markus Glück; Andrey R. Kolovsky; Hans Jürgen Korscharticlehttps://kluedo.ub.uni-kl.de/frontdoor/index/index/docId/1062Fri, 10 Mar 2000 00:00:00 +0100